introduction to fungi mw% +

Question 1

What is a fungus?

Answer 1

• A chemo-organotrophic eukaryote that lacks chlorophyll and forms spores.
• Its cell wall contains polysaccharides, often chitin or glucan, and it absorbs nutrients.
• Its membrane contains ergosterol as the major sterol.
• Classification is principally based on morphology.
• Informally we refer to the major types as moulds, yeasts or mushrooms

Question 2

Yeasts

Answer 2

• Fungi that favour a unicellular habit

Question 3

The fungal kingdom

Answer 3

• Fungi from all 3 groups can cause disease in humans
• Mycytes

Question 4

Dermatophytosis

Answer 4

Moulds with a tendancy to degrade keratin (protein that protects epithelial cells from damage or stress) as a nutrient source.

Causative agents ►:Epidermophyton, Microsporum and Trichophyton spp.

Question 5

Fungi are a significant cause of non-fatal diseases

Answer 5

Athlete’s foot: caused by Epidermophyton, Microsporum and Trichophyton spp.

Thrush: caused by Candida spp.

Pityriasis versicolor: caused by Malassezia spp.

Question 6

Fungal infections

Answer 6

Acting as opportunistic pathogens of immunocompromised patients such as:

• Candida species
• Aspergillus spp

Question 7

Candida species

Answer 7

• Infect deep organs of patients with various types of immune dysfunction, e.g. after abdominal surgery, burns, etc

Question 8

Aspergillus spp

Answer 8

Infect deep organs of patients undergoing chemotherapy, stem cell transplantation

Question 9

Describe the host factors that contribute to the pathogenicity of fungal infections?

Answer 9

• Favourable micro-environments encourage growth of fungi on skin and mucous membranes
• Broad-spectrum antibacterial agents reduce competition for epithelial colonization sites in the gut
• Immunosuppression of all types may create a window of opportunity for fungal invasion

Question 10

Candida and candidiasis

Answer 10

• Worldwide distribution. Candida species commensal to GI tract, some are environmental. Most infections are endogenous.
• Candida spp. are yeasts

Question 11

Candida infection

Answer 11

Superficial: mouth, vagina, penis, skin, nails

Deep-seated:disseminated infections in immunocompromised hosts(abdominal surgery, major burns, etc.)

Question 12

Aspergillosis

Answer 12

• Aspergillus spp. are moulds
• They are ubiquitous in the environment: infection occurs by inhalation of conidia
• These fungi are strongly angioinvasive (penetrate the walls of blood vessels)

Question 13

Cryptococcosis

Answer 13

Question 14

Describe the diagnostic methods for detecting fungi?►

Answer 14

• Direct detection such as histopatholgy (tissue examination) and high resolution CT-scan.
• Direct smear
• Detection of circulating fungal antigens
• Detection of circulating antibodies to fungi
• PCR for fungal DNA
• Culture of fungus from normally sterile site